This invention relates to a catheter, and in particular to a composition used in a torsion control catheter.
Torsion control catheters, such as angiographic or guiding catheters, are designed for intravascular use in the treatment of disease and typically have a soft, flexible tip member connected to a tubular body. The body is formed of a relatively stiff material such as a nylon or a stiff polyurethane to provide torqueability, burst pressure strength and longitudinal rigidity sufficient to advance the catheter in arteries and other tortious pathways in the body.
Torsion control catheters must be able to transmit a twisting or torsional force along their length to permit twisting forces applied at a proximal end portion of the body to be transmitted along the longitudinal axis of the catheter to the distal end portion of the body at which the tip is disposed. In this way, the catheter can be guided through arteries and the like. However, in doing so, the twisting and forward movement of the catheter poses a risk of injury or trauma to the surrounding tissue. Accordingly, it is generally desirable for such catheters to have a soft tip on one end of the body which is more flexible than the body. The soft tip prevents injury to the vessels and arteries as the catheter is advanced in the body and facilitates the guidability of the catheter.
Various polymer compositions for catheter bodies and for catheter soft tips have been proposed. Many of the catheter soft tips formed from these compositions suffer from limitations inherent in the thermal and/or physical properties of the tip materials. For example, some materials, such as polyamide block copolymers, exhibit too much memory. As a result, tips made from these materials tend to want to retain their shape, and may cause trauma to vessels when advanced in the body and may hinder guidability. Other materials do not bond well to commonly preferred body materials, or may become too soft at body temperature.
The present invention is directed to a catheter employing a soft tip having advantageous thermal and physical properties that overcome the problems associated with prior art catheters.